Without biosecurity, higher crop yields mean better-fed rodents

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David Cook does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

FOOD SECURITY - With a global population tipped to exceed 9.2 billion by 2050, the security of the world’s food supplies is more fraught now than ever. But can we do more to protect the food we have?

While the total land area devoted to food production has remained steady at around 15.5 million square kilometres since the 1960s, in recent years we have been losing about 1% of this land annually because of degradation, desertification, urban sprawl, mining, recreation, toxic pollution and rising sea levels.

Despite these pressures on land availability, or perhaps because of them, the amount of cereal crops we produce has increased over the past 50 years.

This is because scientists have been successfully developing technologies to increase the amount of food produced from a given area of farm land using breeding and cloning techniques and genetic modification.

But, the rate at which yields have been improving from year to year has been in decline for the past 25 years. In fact, wheat yield growth has averaged only 1% per annum since 1970 in the developed world, equivalent to an additional 4 million tonnes of wheat per year.

There are many institutions around the world developing high-yielding crop varieties, including Australia’s own CSIRO which is a world-leader in terms of plant breeding research.

But, we can’t rely on increased yields alone. We need to broaden our approach and implement additional strategies in order to maximize the benefits from improved breeding and ensure that more of what we grow gets to where it is most needed.

Biosecurity may be the way. Often overlooked in the continual struggle to produce more, biosecurity aims to protect agriculture from all manner of invasive species, be they vertebrates, weeds, insects or pathogens.

A recent US study showed that invading species cause losses adding up to almost $120 billion per year nationwide. In Australia, weed invasion alone costs agriculture $3.9 billion per year.

Moreover, the spread of invasive plants is now ranked second, behind species extinction, as the greatest threat to ecosystem functions worldwide.

To give some examples of the sort of damage invasive species can inflict, rodents eat about 6% of the annual Indonesian rice harvest: that’s enough rice to feed Indonesia’s 240 million people for a year.

The fungal pathogen black sigatoka (Mycosphaerella fijiensis) can reduce banana yields by half. Witchweed (Striga hermonthica) has invaded 20-40 million hectares of arable land in sub-Saharan Africa and reduced crop yields by more than 20%.

Weeds in general have the potential to reduce global wheat yields by 18-29%. Another fungus, the appropriately named rice blast (Magnaporthe oryzae) kills off enough rice to feed 60 million people per year.

If they are not controlled, weeds, plant pathogens, vertebrate and invertebrate pests wipe out between 50 and 80% of pre-harvest yield amongst the world’s staple crops.

Even with controls, losses may still be as high as 30-40%. With just a minor improvement in biosecurity, the supply of food can be dramatically increased.

Exotic species are a key contributor to cereal losses. Of these, plant pathogens account for almost half of the projected damages. Recently, CSIRO has developed pest impact computer simulation models to quantify the benefits of protecting global wheat supplies from exotic plant pathogens.

Slowing the spread of the Ug99 fungus to 15 of the world’s top wheat producing countries could generate annual benefits in excess of $4.5 billion. That means an annual increase in the global wheat harvest of 46.8 million tonnes.

To get this much extra wheat through crop breeding, average yields would need to increase by approximately 7%. This is more than all the gains from the past 40 years of crop breeding and engineering.

The numbers are impressive, but getting the message across to world leaders and food aid agencies hasn’t been wildly successful. Expanded international trading protocols and improved transport or storage technologies can be a hard sell next to the innovative plant breeding exploits of some very clever scientists.

Protecting the food we already produce often involves the application of existing, and sometime old “tried and tested” technologies, rather than cutting edge science.

Simple improvements in storage facilities to rodent proof them, adoption of on-farm hygiene practices by managers, and even the simple prevention of leakage from transport containers can have a very large effect on the supply of food.

Meeting future food demands presents a huge challenge, and unless we can work towards complementary approaches to maintaining the integrity of food supply chains, it could prove the makings of an unprecedented humanitarian disaster.

But if the food security and biosecurity communities work together to provide innovative and effective food supply strategies, then it could produce one of humanity’s finest achievements.